A complex site that stretches for over 100 km from the River Forth at Stirling eastwards past Edinburgh, and along the coasts of Fife and East Lothian before culminating in a wide mouth. The IBA covers large areas of intertidal flats and inshore waters, in addition to saltmarsh and sand-dune systems, maritime grassland, heath and fen. The IBA is important for wintering and passage wildfowl and waders, and for breeding terns.